The present invention relates to analog and digital circuits. In particular, the present invention relates to a bootstrap capacitor low voltage prevention circuit.
Bootstrap capacitors are commonly used in many electronic circuits. A bootstrap capacitor charging circuit typically charges a bootstrap capacitor when a signal, such as a voltage, goes below a predefined threshold. On the other hand, when the signal is above the predefined threshold the bootstrap capacitor is not charged. Therefore, the amount of charging time for a bootstrap capacitor is the amount of time the signal is below the predefined threshold.
In some operating conditions, the bootstrap capacitor may not be charged to a sufficient value to provide a stable signal to drive a circuit. This can cause a circuit to become non-operational. For example, if a bootstrap capacitor is not charged sufficiently, a switch may be left on in a weak state. This can result in the circuit being uncontrollable. Additionally, if the switch is left on, voltages in the circuit may rise above the intended values causing an over voltage condition.
The present invention is directed at addressing the above-mentioned shortcomings, disadvantages and problems, and will be understood by reading and studying the following specifications.
In accordance with aspects of the present invention, an apparatus and method are provided for a bootstrap capacitor low voltage prevention circuit.
In one aspect of the invention, a switched voltage is coupled to a switching regulator circuit that outputs an output voltage and provides a feedback signal to a control logic circuit. The control logic circuit measures the voltage across a bootstrap capacitor and controls the operation of the switched voltage as well as charging the bootstrap capacitor depending on the state of the switch.
Another aspect of the invention includes an over voltage protection circuit and temperature shutdown circuit. If an over voltage condition is detected the circuit is returned to a state of normal operating conditions. Similarly, if the circuit reaches a predetermined temperature, the circuit is shut down.
Yet another aspect of the invention includes a method of controlling a bootstrap capacitor low voltage prevention circuit. In accordance with this aspect, the voltage across a bootstrap capacitor is measured. When the measured voltage is too low, the charging of the bootstrap capacitor is stopped, a switched voltage is drained to a predetermined level, and the bootstrap capacitor is charged to a predetermined level.
Still yet another aspect of the invention includes a circuit and method for analyzing a waveform. A signal is analyzed to determine if the bootstrap capacitor should be drained or charged. In accordance with this aspect of the invention, the bootstrap capacitor is not charged unless the value of the signal drops below a predetermined threshold.